1. Technical Field
The present invention relates to a photomask defect correcting method and device.
Priority is claimed on Japanese Patent Application No. 2007-210362, the content of which is incorporated herein by reference.
2. Related Art
Conventionally, as a defect correcting method and device used for correcting a defect of a photomask, a method and device are known for performing correction of a opaque defect and correction of a clear defect using an etching capability of a minute region using a focused ion beam and an ion beam-induced chemical vapor deposition capability. As the focused ion beam, gallium ion beam using a liquid metal gallium ion source has been used. However, a Ga ion is opaque with respect to light which has a wavelength of 193 nm and is currently used for exposing a leading-edge mask. Accordingly, since the Ga ion is injected into a glass or quartz substrate which is a light transmission portion, transmissivity of the light transmission portion is decreased and thus there is the deterioration in the optical characteristics of a defect correction point or an observed region.
The injected Ga ions can be removed to some degree by wet cleaning, but cannot be completely removed if the injection amount thereof is large. Accordingly, there is a restriction in the number of observations, and additional processing in the vicinity of a correction point has been difficult. That is, since the Ga ions are injected and accumulated whenever an observation is performed (the ion bean is scanned), after cleaning, a restriction is set on the number of observations so that the Ga ions are not accumulated to a degree that the necessary transmissivity cannot be obtained. In addition, additional processing is performed where a region including a defect is once more observed after the correction of the defect and an uncut portion or a loss portion of the defect is recorrected or a removing reattachment is performed. However, although a shape is improved due to the additional processing, the injection amount of the Ga ions is increased because the observation is performed once more and additional processing is performed. Thus, even when cleaning is performed, the Ga ions are accumulated to a degree that the transmissivity is not recovered.
In addition, since the used wet cleaning removes the Ga ions by selectively cutting glass or quartz of a Ga-ion injection portion (see Non-Patent Document 1), the glass or quartz is scrapped by being cleaned a plurality of times such that there is a phase difference between a scrapped portion and a portion that is not scrapped. Thus, since the optical characteristics of a light transmission portion deteriorate, it is difficult to perform recorrection.
Non Patent Citation 1: Y. Itou et al., “Proc. of SPIE”, (US), 2005, 5992, p. 59924 Y-1-59924 Y-8
In a photomask defect correcting method and device using a conventional liquid metal ion source, there is a problem that the transmissivity of the light transmission portion is deteriorated by the injection of the Ga ions and there is a restriction in that additional processing cannot be performed in order to avoid the deterioration of the transmissivity.
In order to avoid the injection of the Ga ions to the transmission portion when correcting the defect, for example, an electron beam may be used. However, when using an electron beam, a sample is apt to be charged up and processing efficiency is bad.